This application claims the priority of German application No. 101 08 057.3, filed Feb. 20, 2001, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a method for quenching metallic workpieces in a furnace space, especially at above-atmospheric pressure. An inert gas or a mixture of inert gases, especially nitrogen, argon and/or helium are a used as quenching gas (mixture), after the metallic workpiece has been subjected to a heat treatment process in an evacuated furnace space.
Generic methods for quenching metallic workpieces are known. At high temperatures, especially at temperatures above 700xc2x0 C., metals react very sensitively to oxygen. For example, at 1000xc2x0 C., chromium is oxidized already at an oxygen partial pressure of about 10xe2x88x9223 bar. Moreover, higher contents of, for example, titanium, result in an undesired formation of nitride, because of which heat treatment cracks can occur.
For a large number of quenching processes, a forming gas is used, which consists of about 5% hydrogen and about 95% nitrogen. By this forming gas, a slight surface oxidation is achieved on the metallic material that is to be treated and, moreover, the work is carried out below the explosive limit.
It is an object of the present invention to create a method for quenching metallic workpieces, for which annealing colors and oxidation phenomena at the surfaces of metallic workpieces can be reduced or avoided. Moreover, the absorption of nitrogen, as well as the nitride formation mentioned, are to be reduced.